[linux-lvm] LVM snapshot - "dd" file size

[Thomas Bellembois]

Nice tip ! It works fine !
Thanks a lot.

Ragards,

Thomas

Denie Andriessen wrote:
> A compressed dd can still be quite large, as there still might contain
> non zero values..
>
> if you compress the image, a possible way to make the resulting files
> smaller is to:
>
> - do a: 'dd if=/dev/zero of=/dummyfile' on the filesystem first (you
> might want to use 'bs' and 'count' parameters)
> - if you topped off the disk, delete the all zero dummyfile.
>
> The zipped result might be smaller. (both with dd and with tar..)
>
> Regards,
> Denie
>
> ----- Original Message ----- From: <dave at frop.net>
> To: "LVM general discussion and development" <linux-lvm at redhat.com>
> Sent: Wednesday, April 16, 2008 11:04 PM
> Subject: Re: [linux-lvm] LVM snapshot - "dd" file size
>
>
>> this has nothing to do with LVM.
>>
>> dd knows nothing about files, it just copies the entire device (or
>> file or whatever).
>>
>> tar will work, if you use the right command line switches. Search
>> around on the web for pointers on how to use it.
>>
>> Another intermediate way would be to compress the image you get with dd.
>>
>> On Wed, Apr 16, 2008 at 04:59:05PM +0200, Thomas Bellembois wrote:
>>> Hi!
>>>
>>> I am using LVM partitions on a Debian Xen system.
>>> I use LVM snapshots to clone and backup my virtual machines.
>>>
>>> I have noticed that the ISO file created with the "dd" command it much
>>> bigger that the partition used space (actually 4.7GB for the ISO -
>>> 500MB
>>> used space). No problem if I mount the LVM snapshot and "tar" all of
>>> the
>>> data.
>>>
>>> I have googled the question and read that "dd" also copy "not used
>>> space".
>>> Why is the ISO file so big ? Is the "tar" method less safe ?
>>> Is there a better solution ?
>>>
>>> Thanks for your answers.
>>>
>>> Regards,
>>>
>>> Thomas
>>>
>>>
>>>
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>>> linux-lvm at redhat.com
>>> https://www.redhat.com/mailman/listinfo/linux-lvm
>>> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>>
>> _______________________________________________
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>>
>
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